Actinomyces naeslundii forms plaque and is an important agent in human root caries and periodontal disease. Plaque formation is a primary pathogenic property of those organisms which cause these oral diseases, and elimination of plaque formation by A. naeslundii will decrease or inhibit its pathogenicity. Although A. naeslundii has the potential to form plaque under a variety of nutritional conditions, essentially nothing is known about the specific attachment mechanisms involved. The objective of the proposed research is to define the mechanisms by which A. naeslundii forms plaque. The approaches to this objective are: 1. standardization of adherence and aggregation assays; 2. determine the ability of substances to induce adherence and aggregation; 3. analyze products released from enzymatic degradation of A. naeslundii plaque; 4. chemically analyze materials extracted from A. naeslundii plaque and test their ability to induce adherence and aggregation; 5. detect the presence of cell-surface polymer binding sites by enzymatic degradation studies. The long-term goal of the proposed research is to approach prevention of plaque-associated oral diseases. The specific information gained from this research will provide a logical basis for the clinical use of substances or techniques to reduce the incidence of root caries, periodontal disease and coronal caries. This will increase the capacity of the clinician for the delivery of dental health care.